1. Field of the Invention
The disclosure relates generally to remote control systems, and specifically to a universal remote control transmitter that can acquire the transmission frequency and modulation pattern of another transmitter without prior knowledge of these parameters.
2. Background of the Invention
Transmitter-receiver controller systems are widely used for remote control and/ or actuation of devices or appliances such as garage door openers, gate openers, security systems, and the like. For example, most conventional garage door opener systems use a transmitter-receiver combination to selectively activate the drive source (i.e., motor) for opening or closing the door. The receiver is usually mounted adjacent to the motor and receives a coded signal (typically radio frequency) from the transmitter. The transmitter is typically carried by a user and selectively activated by the user to open or close the garage door. These type of remote control systems typically employ VHF/UHF radio frequency transmissions.
In general, a remote control system has a remote transmitter and a receiver coupled to the device, which is to be controlled. When activated, the transmitter emits a modulated signal, which is recognized by the receiver to activate the device. In VHF/UHF-based systems, a transmitter typically emits a pulse-modulated VHF/UHF signal. The signal embodies a modulation pattern as a sequence of “signal on” and “signal off” intervals. The modulated signal emitted by the transmitter is recognized by the receiver. The modulation pattern of remote control systems is typically unique to restrict unauthorized access to the device being controlled.
Different manufacturers of such transmitter-receiver systems generally utilize different transmission protocols or patterns for transmitting the coded signal. Additionally, the manufacturers typically operate the transmitter-receiver systems at different transmission frequencies within the allocated frequency range for a particular type of system. The modulation pattern typically includes two aspects: 1) a device code (equivalent to a device address) for the transmitter and receiver, and 2) a transmission format, i.e., the characteristics of the transmitted signal including timing parameters and modulation characteristics related to encoded data. The transmission pattern used by one manufacturer is usually incompatible with that provided by other manufacturers.
Currently available transmitter-receiver systems typically employ custom encoders and decoders to implement the transmission pattern. These encoders and decoders are fabricated with custom integrated circuits such as application-specific integrated circuits (ASICs). They are fixed hardware devices and allow very limited flexibility in the encoding/decoding operation or in the modification of the encoding/decoding operation.
Thus, in such existing transmitter-receiver systems, it is necessary to know the transmission frequency accepted by the receiver and to match or determine the modulation pattern recognized by the receiver. In a number of transmitter-receiver systems, the modulation pattern is determined by setting a plurality of dual inline package (DIP) switches (or a modulation pattern selection circuit) on the transmitter and by similarly setting a plurality of DIP switches (or a corresponding modulation pattern selection circuit) on the receiver. Once the required frequency and the modulation pattern are defined, a compatible transmitter can be provided to operate with the receiver. The DIP switches or the modulation pattern selection circuit may also be manually reset to match the modulation pattern of signals transmitted by a new transmitter to that of the existing receiver. Alternatively, both the existing receiver and new transmitter can be reprogrammed with a new modulation pattern. However, existing reprogramming techniques require prior knowledge of the transmission frequency and modulation protocol of the existing transmitter. In addition, they can only be implemented in compatible transmitters and receivers using complex circuits.